package config

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strings"
)

// ParseEnvFileKeys 用与 applyEnvFile 相同的解析规则列出文件中出现的键。
func ParseEnvFileKeys(path string) ([]string, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	var keys []string
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		parts := strings.SplitN(line, "=", 2)
		if len(parts) != 2 {
			continue
		}
		keys = append(keys, strings.TrimSpace(parts[0]))
	}
	return keys, scanner.Err()
}

// FormatFieldSources 渲染字段级来源表（KTD17：只报告来源/状态，不打印值）。
func FormatFieldSources(entries []FieldSource) string {
	var b strings.Builder
	b.WriteString("field                                 layer                set\n")
	for _, e := range entries {
		fmt.Fprintf(&b, "%-37s %-19s %v\n", e.Field, e.Layer, e.Set)
	}
	return b.String()
}

// SortedFieldSourceNames 返回已知来源字段名（测试辅助）。
func SortedFieldSourceNames(m map[string]FieldSource) []string {
	names := make([]string, 0, len(m))
	for k := range m {
		names = append(names, k)
	}
	sort.Strings(names)
	return names
}